Numerous accidents are caused each year by someone moving a ladder which is in use. This is particularly true in industrial applications where service work must be performed by someone standing on a ladder and the day in and day out presence of the ladder and its frequent use gives rise to a certain amount of carelessness and numerous injuries result.
Another problem is in descending the ladder, once again as a result of familiarity, the user will often believe that he is stepping on the last rung of the ladder whereas he is in fact stepping on the second to last or third to last rung. He then steps off that rung expecting to step on the floor and instead the floor is not where he expects, and the result is often a sprained ankle or other injury.
In many applications such as telephone company switching rooms, the user places a sign on the ladder when he is working from the ladder but unfortunately occasionally the sign is not noticed and further occasionally the sign is not used.
There is thus a need for an automatic system which does not require the user to take any overt act and which is more noticeable than a sign. Also, there is a need to provide a positive signal when the user steps on the lowermost rung of the ladder to prevent the possible injury described above.